This invention relates generally to materials segregating apparatus and has particular reference to apparatus for segregating selected conductive nonferromagnetic metals from a mass or supply of commingled nonferromagnetic materials.
Solid municipal waste may be shredded and then classified into light and heavy fractions, each having therein items suitable for recycling. The light fraction, for example, usually includes paper and cardboard which may be used in the production of new paper products or may be sold as combustible fuel. The heavy fraction generally is comprised of glass, ceramic, wood, ferromagnetic materials, and nonferromagnetic materials for examples. The ferromagnetic materials may be extracted by conventional means, such as electromagnets, and subsequently used in the manufacture of steel and other metal alloys.
The heavy fraction of nonferromagnetic municipal waste includes at least two other categories of potentially saleable items, namely nonferromagnetic metals and clean glass. The nonferromagnetic metal component of the heavy fraction generally is comprised of aluminum scrap, copper-zinc base scrap, and tin scrap, for examples. Market analysis indicates that there is a greater demand for the nonferromagnetic metals than for other components of the heavy fraction. Thus, although constituting only a small percent by weight of typical municipal waste, the nonferromagnetic metals nevertheless represent a significant percentage of the total resale value.
Of the total nonferromagnetic metal content, aluminum constitutes an important part, and at the present time it is aluminum which receives the most attention since is usually provides the highest value per ton of municipal trash.
Accordingly, prior art means have been developed for separating nonferromagnetic metals from other components of municipal waste. These prior art means generally involve heavy media separation, electrostatic separation, or electromagnetic separation.
However, heavy media separation has not been generally satisfactory due in part to fluids becoming entrapped in the crushed items of municipal waste and erratically affecting their specific gravities. Electrostatic separation generally requires the use of complicated apparatus for establishing a strong electrostatic field which induces electrostatic charges on respective items of municipal waste. Electromagnetic separation generally involves the use of sophisticated electrical equipment and circuitry for producing a time varying electromagnetic field which induces eddy-currents in the nonferromagnetic metal objects in municipal waste.
Therefore, it is advantageous and desirable to provide materials separating apparatus with simple and relatively inexpensive means for segregating the nonferromagnetic metal items in commingled waste materials. Such separation apparatus is shown and described in copending U.S. patent application Ser. No. 552,576 filed Feb. 24, 1975, which is a continuation-in-part of abandoned application Ser. No. 509,203, filed Sept. 25, 1974 by E. Schloemann. This copending application describes a material separating apparatus which comprises means for directing commingled nonferromagnetic materials including conductive metals into a stream which is intercepted by an alternating series of oppositely directed magnetic fields. These fields induce eddy currents in the conductive materials and thus exert forces such as will split the stream into a number of streamlets containing materials of different conductivity characteristics. The streamlets then are gathered into a respective supply of segregated materials.
However, apparatus such as described in the aforementioned copending application is suitable for processing only a relatively small amount of material in any given period of time.